Controle a rotation continue servo motor

Your Right, it's not exactly the position I need to control...

I have to control the angle, like with a standard "servo 180°"

I maked a little robot with 2 FS90R, I thought I could also control the angles to make it go wheel turn by wheel turn. I did not know that the "continue servo motor" were so different to control than the "180° servo"...

I want to program a way to my robot, for example : 3 turn of wheels, rotation 90° right, 8 turn of wheels, rotation 90° left, 8 turn of wheels...

Do you know if it's posible ?

Thank you...